The present invention relates to a breather device of an engine of a vehicle.
Generally, in an engine of a vehicle, gas accompanied by pressure generated in a cylinder bore of the engine leaks into a crankcase by little or trace amount through a clearance between a piston and the cylinder bore. As the pressure of the gas in the crankcase incessantly changes according to the sliding motion (displacement) of the piston, if the crankcase is airtight, the pressure of the gas in the crankcase, i.e., so-called blow-by gas, interferes with the movement of the piston. It is, therefore, necessary to provide means, such as breather device, for releasing the blow-by gas in the crankcase and separating an oil content atomized and mixed into the blow-by gas from the gas.
In order to separate the atomized oil content mixed from the blow-by gas, it is necessary to form a breather chamber having a predetermined inner volume. It is, however, difficult for the layout to form the breather chamber having the sufficient volume for an engine of a diminutive vehicle having compact size according to one of development objectives. Therefore, in order to secure the sufficient volume of the breather chamber, in the prior art, there is proposed an arrangement in which a breather tank is located outside the engine.
A general arrangement in the prior art such as mentioned above is shown in FIGS. 10 and 11.
With reference to FIGS. 10 and 11, a breather tank 8 is arranged in a space surrounded by a crankcase 2 and a cylinder head 3 of an engine 1, an air cleaner 4 which constitutes an intake system, an outlet tube 6 extending from the air cleaner 4 towards a carburetor 5 disposed at a rear portion of the cylinder head 3, and an exhaust pipe 7 which constitutes an exhaust system provided on one side of the engine 1.
In a recent structure, the blow-by gas is caused to circulate in the air cleaner 4 for carrying out re-combustion to thereby prevent air pollution.
However, the outlet tube is normally made of an elastic material so as to improve the assembling property of the tube and is, therefore, sometimes inferior in heat resistance. In addition, the outer surface temperature of the exhaust pipe becomes elevated since high temperature exhaust gas passes through the interior of the exhaust pipe.
As a result, it is required for the outlet tube and the exhaust pipe to be separated in arrangement from each other. Thus, the width of the vehicle increases, and the space between the outlet tube and the exhaust pipe constitutes a dead space, being inconvenient and not advantageous.
The present invention was conceived in consideration of the circumstances in the prior art mentioned above, and it is therefore an object of the present invention to provide a breather device of a vehicle engine capable of shutting off an intake system from heat of an exhaust system and making effective use of a dead space between an outlet tube of the intake system and an exhaust pipe of the exhaust system.
This and other objects of the present invention can be achieved by providing a breather device of an engine of a vehicle in which an engine including a crankcase and a cylinder assembly, which comprises a cylinder block arranged on an upper surface of the crankcase, a cylinder head and a cylinder cover, is mounted to a vehicle body frame, an engine intake system is arranged on a rear side of the cylinder assembly, an engine exhaust system is arranged on one side of the engine, and a breather device is arranged in the vehicle body so as to release a blow-by gas in the crank case and to separate an oil content in the blow-by gas therefrom, the breather device comprising:
a breather tank arranged independently between the engine intake system and the engine exhaust system on the rear side of the cylinder assembly and above the crankcase; and
a plurality of breather pipes connecting the breather tank to the engine and the engine intake system.
In a preferred embodiment of this aspect, the breather tank may be arranged between an outlet tube of the engine intake system and an exhaust pipe of the engine exhaust system.
The breather tank has a side surface which faces the engine intake system and is curved along an outer configuration of the engine intake system. The breather tank is provided with a plurality of breather chambers formed therein by dividing an interior thereof by means of partition walls so as to communicate with each other, and unions for connection to the breather pipes are arranged respectively to the breather chambers. The breather tank is arranged just above the crankcase, a further breather chamber is arranged in an upper portion of the crankcase directly under the breather tank, and the further breather chamber is communicated with the one of the plural breather chambers in the breather tank through one of the breather pipes.
The breather pipes are arranged so as to be curved and arranged at positions higher in height level than an entire structure of the engine including the engine intake system and the engine exhaust system.
The engine intake system includes air cleaner provided, at an upper portion thereof, with an intake duct extending obliquely forward towards upward, the intake duct having an intake port at an upper end of the intake duct, and the breather tank is disposed in parallel to the intake port as viewed in a plan view and arranged between the intake port and the engine exhaust system and above the engine exhaust system.
According to the breather device of a vehicle engine of the characters mentioned above, the breather tank functions as a heat shielding member to make it difficult to transfer the heat emitted from the engine exhaust system to the engine intake system. Therefore, it is possible to arrange the engine exhaust system and the engine intake system more proximately to each other, reduce the width of the vehicle and make effective use of the dead space in the vehicle body.
It is therefore possible to sufficiently secure the volume of the breather tank even in narrow space for location and improve gas-liquid separation performance, and in addition, an easy arrangement of the breather pipe can be also made possible.
Furthermore, the separated oil content can smoothly return to the engine and the engine starting operation can be done with substantially no failure, improving the output power performance of the engine.
The nature and further characteristic features of the present invention will be made more clear from the following descriptions made with reference to the accompanying drawings.